RNA-mediated interaction of Cajal bodies and U2 snRNA genes

Cajal bodies (CBs) are nuclear structures involved in RNA metabolism that a ccumulate high concentrations of small nuclear ribonucleoproteins (snRNPs). Notably, CBs preferentially associate with specific genomic loci in interp hase human cells, including several snRNA and histone gene clusters. To unc over functional elements involved in the interaction of genes and CBs, we a nalyzed the expression and subcellular localization of stably transfected a rtificial arrays of U2 snRNA genes. Although promoter substitution arrays c olocalized with CBs, constructs containing intragenic deletions did not. Ad ditional experiments identified factors within CBs that are important for a ssociation with the native U2 genes. Inhibition of nuclear export or target ed degradation of U2 snRNPs caused a marked decrease in the levels of U2 sn RNA in CBs, and strongly disrupted the interaction with U2 genes. Together, the results illustrate a specific requirement for both the snRNA transcrip ts as well as the presence of snRNPs (or snRNP proteins) within CBs. Our da ta thus provide significant insight into the mechanism of CB interaction wi th snRNA loci, strengthening the putative role for this nuclear suborganell e in snRNP biogenesis.